Liquid crystal compounds having a terminal 1-alkynyl residue

Abstract

Compounds of the formula <IMAGE> I wherein n stands for the number 0 or 1; rings A, B and C each independently represent trans-1,4-cyclohexylene, trans-1,3-dioxane-2,5-diyl or unsubstituted or fluoro-substituted 1,4-phenylene; R1 denotes 3E-alkenyl with 4 to 12 carbon atoms, 4-alkenyl with 5 to 12 carbon atoms or, when ring A represents trans-1,4-cyclohexylene or trans-1,3-dioxane-2,5-diyl, also 1E-alkenyl with 2 to 12 carbon atoms; and R2 is hydrogen or C1-C10-alkyl, their manufacture as well as liquid crystalline mixtures which contain such compounds and their use for electro-optical purposes.

We claim: 
     
       1. A compound of the formula ##STR8## wherein n stands for the number 0 to 1, rings A, B and C each independently represent trans-1,4-cyclohexylene, trans-1,3-dioxane-2,5-diyl or unsubstituted or fluoro-substituted 1,4-phenylene, with the proviso that no more than one trans-1,3-dixoane-2,5-diyl ring is present in the compound; R 1  is a 3E-alkenyl with 4 to 12 carbon atoms, a 4-alkenyl with 5 to 12 carbon atoms or, when ring A represents trans-1,4-cyclohexylene or trans-1,3-dioxane-2,5-diyl also a 1E-alkenyl with 2 to 12 carbon atoms; and R 2  is hydrogen or C 1  -C 10  alkyl. 
     
     
       2. A compound according to claim 1 having one of formulas ##STR9## wherein X 1  and X 2  each independently represent hydrogen or fluorine; R 2  is hydrogen or C 1  -C 10  -alkyl; and R 1  is one of a 3E-alkenyl with 4 to 12 carbon atoms, a 4-alkenyl with 5 to 12 carbon atoms. 
     
     
       3. A compound according to claim 1, wherein R 1  is a straight-chain residue; and R 2  is hydrogen or a straight-chain residue. 
     
     
       4. A compound according to claim 1 wherein R 1  has a maximum of 7 carbon atoms. 
     
     
       5. A compound according to claim 1 wherein R 2  is hydrogen or C 1  -C 5  -alkyl. 
     
     
       6. A compound according to claim 5 wherein R 2  is C 1  -C 3  -alkyl. 
     
     
       7. A compound according to claim 1 wherein R 1  denotes 3-butenyl, 3E-pentenyl or 4-pentenyl. 
     
     
       8. A liquid crystalline mixture having at least 2 components, wherein at least one component is a compound of formula ##STR10## wherein n stands for the number 0 or 1; rings A, B and C each independently represent trans-1,4-cyclohexylene, trans-1,3-dioxane-2,5-diyl or unsubstituted or fluoro-substituted 1,4-phenylene, with the proviso that no more than one trans-1,3-dioxane-2,5-diyl ring is present in the compound; R 1  is a 3E-alkenyl with 4 to 12 carbon atoms, a 4-alkenyl with 5 to 12 carbon atoms or, when ring A represents trans-1,4-cyclohexylene or trans-1,3-dioxane-2,5-diyl also a 1E-alkenyl with 2 to 12 carbon atoms; and R 2  is hydrogen or C 1  -C 10  -alkyl. 
     
     
       9. A compound of claim 1 having the structural formula ##STR11##